Inkjet printing systems are in common use today. In one common form for swath printing, the printing systems includes one or more print cartridges mounted on a scanning carriage for movement along a swath axis over a print medium at a print zone. The print medium is incrementally advanced through the print zone during a print job.
There are various print cartridge configurations. One configuration is that of a disposable print cartridge, typically including a self-contained ink or fluid reservoir and a printhead. Once the fluid reservoir is depleted, the print cartridge is replaced with a fresh cartridge. Another configuration is that of a permanent or semi-permanent print cartridge, wherein an internal fluid reservoir is intermittently or continuously refilled with fluid supplied from an auxiliary fluid supply. The auxiliary supply can be mounted on the carriage with the print cartridge, or mounted off the carriage in what is commonly referred to as an xe2x80x9coff-axisxe2x80x9d or xe2x80x9coff-carriagexe2x80x9d system.
Off-axis systems can also take different forms. One form of off-axis fluid delivery system employs flexible tubing to continuously connect between the fluid supply located off-axis and the print cartridge or print head located on the carriage, i.e. on-axis. Another form of off-axis fluid delivery system provides an intermittent connection between the off-axis fluid supply and the carriage-mounted print cartridge, e.g. by moving the carriage to a supply station, where the connection is made.
Typically, each of the existing off-axis forms optimizes particular parameters, such as cost, size, complexity, delivered ink (usage scalability), packing density, air management, number of inks, printhead life, and user intervention rate. As the inkjet market matures, customer expectations become more demanding, and there thus exists the need for ink delivery systems that incorporate substantial improvements in many of these areas simultaneously.
A fluid delivery system is described, which includes a print head assembly (PHA) and a fluid supply for intermittent connection to the PHA. In an exemplary embodiment, the PHA includes a PHA body structure, an air-fluid separator structure, a printhead, a fluid plenum in fluid communication with the printhead and the air-fluid separator structure, and a PHA free fluid reservoir. A fluid re-circulation path passes through the separator structure, the plenum and the free fluid reservoir. A pump structure is supported by the PHA body structure for re-circulating fluid through the re-circulation path during a pump mode. The fluid supply includes a supply reservoir for holding a supply of fluid, and is connectable to the PHA to provide a fluid interconnect between the supply reservoir and the PHA fluid reservoir when a pressure differential between the PHA and the supply reservoir is sufficient to draw fluid into the PHA free fluid reservoir to replenish the fluid in the PHA fluid reservoir.
In another embodiment, a method is described for supplying fluid to a print head assembly (PHA) including a PHA housing structure, a capillary structure for holding a supply of fluid under negative pressure, a free fluid chamber, a printhead and a fluid plenum in fluid communication between the capillary structure and the printhead. The method includes:
mounting the PHA on a movable carriage of a printing system;
positioning an fluid supply at a supply location off the carriage including a supply reservoir holding a supply quantity of free fluid;
bringing the print cartridge and fluid supply into mating contact so that a PHA fluid interconnect is engaged with a supply fluid interconnect to provide a fluid interconnect path;
pumping fluid through a closed re-circulation path within a PHA housing structure to pump fluid from a PHA free fluid chamber to a PHA capillary structure to a PHA fluid plenum in fluid communication with a PHA printhead and to the free fluid chamber;
and, with the capillary structure in a fluid-depleted state, using a dynamic pressure differential between said fluid plenum and said free fluid chamber to draw fluid from the fluid supply reservoir through the fluid interconnect path until the capillary structure reaches a less depleted state.